Abstract : Generally available clinical methods were used to treat radiation injured beagles. Massive doses of antibiotics and other prophylactic measures were followed by treatment based on clinical judgment; effectiveness of the medical care was judged by the mortality response. The LD50/60 of beagles receiving treatment was 276 rads of mixed gamma-neutron radiation at 17 rads/minute; the LD50/60 for similarly irradiated beagles receiving no medical treatment was 218 rads. Survival time, symptomatic, hematologic, pathologic, and bacteriologic comparisons were also made. An additional group of irradiated beagles received similar medical care plus intravenously administered leukocyte and platelet concentrates; these dogs responses favorably to treatment following doses as high as 330 rads.